A pipeline controller working on a console in Columbus, Ohio, noted the pressure increase in a pipeline in Lawrence, Massachusetts, one of the three cities where the fires occurred, said Sumwalt CNN's Alison Kosik. He did not say when the pressure increase was noticed.
"Of course we will interview this pipeline controller," he said.
On Saturday, Massachusetts Governor Charlie Baker said most people who had to evacuate their homes in Lawrence, Andover and North Andover could go home on Sunday mornings.
"More than 5,000 customers have restored their power supply, and we expect the vast majority of remaining homes to be finished and cleared for gas tonight," Baker said. "People, unless something unforeseen happens, should be able to return to their homes at 7am tomorrow morning."
The NTSB, which is being investigated for transportation – in this case natural gas – arrived in Massachusetts on Friday morning to investigate the fires and gas explosions and will also study the system operations, operations and safety culture of Columbia Gas and its parent company NiSource , as well as a timeline of events surrounding the fires.
"We are very interested in understanding the operations of Columbia Gas and will review their records, compliance with procedures, procedures, training and oversight of their contractors," Sumwalt said Saturday.
Sumwalt also noted that there are 14 gas regulators in the area and investigators plan to test all of them and make sure they all work properly. He expects the NTSB investigators to stay on the ground for seven to ten days while collecting perishable evidence and conducting interviews.
"Our mission is to find out what happened so we can stop it from happening again," Sumwalt said.
Sumwalt said that they will work to identify a cause for the incident and prepare a preliminary report, but that a full, detailed report on the exact reason for a period of up to two years may be incomplete.
There was no evidence at this time that anything was wrong with the fires, Sumwalt said.
At a press conference on Saturday night, Baker said her recovery has three phases:
• Bring people safely to their homes and restore electricity.
• Assessment of the damage to the low-pressure gas system in the affected area.
• Technicians and other experts check every device that distributes gas.
He called home the returnees to inspect all their devices using natural gas and call the authorities if something was wrong.
Gas pipelines were closed in the three cities. Hundreds of natural gas technicians were scheduled to go to the cities in the coming days to resume gas operation, state officials said.
Jeff Hall, spokesman for the Red Cross, said that on Friday after the explosions and fires on Thursday night, nearly 400 people were in shelters.
"The evacuations are in the thousands," Hall said Friday, adding that he expected many residents to live with friends and families in the area.
Lawrence Mayor Dan Rivera said there are about a dozen families "permanently expelled".
Eversource tweeted on Saturday that it was working to shut down more than 8,000 gas meters, and the company said it predicted on Saturday night that "this critical first phase will be essentially completed".
On Friday, the governor said Columbia was "just insufficiently prepared" to effectively manage relief efforts.
Rivera said of the company, "It just seemed like nobody was responsible, like they were in the weeds, and they've never seen it before."
Utility President Steve Bryant later defended the company's performance, saying the company remained in constant contact with state and federal officials.
"I would say we made that happen as fast as we can," he told reporters. "I do not think anyone else who did that would have been lower than we are at the moment."
Bryant expressed his condolences to the victim's family, apologized for the inconvenience to customers, and said the company "provides all resources that we may be able to repair."
It looked like Armageddon & # 39; s
Thursday night, as homes went up in flames by gas fires, Andover Fire Rescue chief Michael B. Mansfield said the scene "looked like Armageddon."
As pressure for the gas company's representatives swelled to provide answers, Sens. Ed Markey and Elizabeth Warren of Massachusetts called for a congressional hearing on the explosions and fires.
Utility is working with officials to investigate this incident
Columbia Gas Transmission was owned by NiSource until 2015 when the company was spun off into the Columbia Pipeline Group. Later, this company became part of TransCanada.
According to its website, NiSource is one of the largest natural gas providers in the United States and serves more than 3.4 million customers in seven states. The company also provides power, generation and transmission services to nearly 500,000 customers in northern Indiana.
CNN's Lauren del Valle, Laura Ly, Mark Morales, Rob Frehse and Kristina Sgueglia all contributed to the report.